问题
I have a class with a bool data member that is not initialized by the constructor. If I do
cout << x.myBoolDataMember;
where x is an object of this class in which the bool has not been initialized, I sometimes get a random number rather than 0 or 1. (I'm using gcc.) Is this behavior compliant with the Standard?
回答1:
Is this behavior compliant with the standard?
Yes! Using garbage values(uninitialized) in your code invokes Undefined Behavior
回答2:
Yes. An uninitialized variable can have any value.
回答3:
As soon as "<<" operator does not check the bool, this behavior is correct.
The problem here is hidden in the bool itself: program uses more than one bit to store the bool. This is dependent on implementation. Sometimes only one bit can be used to store the bool.
Sometimes more, and it is such a case.
来源：https://stackoverflow.com/questions/2154132/printing-an-uninitialized-bool-using-cout-c